Peterson (2003) online here is an influential study cited by IPCC AR4 purporting to show that the urbanization effect is negligible. It concluded:
Using satellite night-lights—derived urban/rural metadata, urban and rural temperatures from 289 stations in 40 clusters were compared using data from 1989 to 1991. Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures.
AR4 said of this study:
Over the conterminous USA, after adjustment for time-of-observation bias and other changes, rural station trends were almost indistinguishable from series including urban sites (Peterson, 2003; Figure 3.3… One possible reason for the patchiness of UHIs is the location of observing stations in parks where urban influences are reduced (Peterson, 2003).
The 289 stations are not listed in the article and no SI is available. One of our readers inquired about the stations and I wrote to Peterson asking him for the information as follows:
Dear Dr Peterson, could you please provide me a list of the USHCN id numbers of the 289 stations used in Peterson 2003, together with information on how they are allocated to the 40 clusters and how they are classified rural-urban? It would be helpful if you provided an SI with this sort of information. Thanks, Steve McIntyre
As I anticipated, Peterson responded promptly with the list together which I’ve posted up here with some additional information that I’ve collated. The first 5 columns are from Peterson. Peterson did not provide lat-long’s; I looked these up in the state files at http://www.wrcc.dri.edu/inventory/sodca.html (CA) etc. I also compared the ID numbers to USHCN id numbers and marked the USHCN-overlapping series. Peterson added the following additional comments:
a) If you read the article, you will notice that I did not specifically use USHCN stations in the analysis.
b) If you read the article, you will notice that I did not classify the stations as rural or urban. That was done by Owen et al. (1998) based on night lights data and used by Gallo and Owen (1999). Kevin Gallo provided me with the metadata he used in Gallo and Owen. I’m sure Dr. Gallo would be happy to answer any questions you might have that are not already addressed in those two papers.
c) The attached file is a list of the 289 stations I evaluated and processed for Peterson 2003. The first number is the group, 1-40; the second column is the rural/urban satellite nigh lights based metadata classification; the third column is the station number and the fourth the station name. If you read Peterson and Owen (2005) you will come across this statement: “The mean urban minus rural difference is 0.03°C using adjusted data and 0.00 with the modified adjusted data. The first result differs slightly from the 0.04°C reported in Peterson (2003) with the difference due to correcting a processing error in the metadata assignments at a few of the stations.” The metadata I provided you are the corrected metadata.
Of the 289 stations, only 63 came from the USHCN network.
In the article, Peterson said that 85 of these stations were rural, 191 urban, and 13 suburban. In the file, there were 84 rural, 6 suburban and 199 urban. Although Peterson attributed the 40 clusters to Gallo and Owen 1999, that article only used 28 clusters and not all of the 28 clusters could be identified in the Peterson list. So some additional selection procedure has been applied.
I did some cross-analyses of the 63 USHCN stations in the Peterson network – the USHCN network being said elsewhere to be mostly “rural”. Of these stations, 13 were rural, 2 suburban and 48 urban.
On an earlier occasion, I did a concordance of USHCN identification numbers to GISS lights – such concordances take a surprising amont of time and I used this information to cross-check GISS lights against Peterson’s network – with the usual surprising results. Of the 63 USHCN stations in the Peterson network, 9 had GISS-lights of 0. However, 3 of the 9 sites with lights=0 were classed by Peterson as urban (Fort Yates ND; Utah Lake Lehi UT; Fort Valley AZ) while 6 were classified as rural.
Of the 13 Peterson USHCN sites classified as “rural”, the GISS lights were as high as 19. Checking the 48 Peterson USHCN sites classified as “urban”, 15 had GISS lights less than or equal to 19 (including 3 with lights=0 as noted above.)
One of the Peterson clusters is in California, where surfacestations.org has a strong survey presence. Here Peterson compared 7 sites classified as “urban”: USHCN sites DAVIS 2 WSW EXP FARM, Lodi; non-USHCN urban sites: Placerville, Sacramento FAA AP, Sacramento WSO City, Antioch Pump Plant, Folson Dam; against one rural non-USHCN non-GHCN site: Camp Pardee. I’m not sure what exactly this proves. If the USHCN is supposed to be a “high quality” network, it’s puzzling that so many sites in the Peterson network do not come from either this network or the GHCN network.
In a follow-up email, Peterson said that the data could be obtained from http://www.ncdc.noaa.gov/oa/mpp/digitalfiles.html which unfortunately is a pay-for-view site. JerryB observed that most of the identification numbers could be matched in the GHCND station inventory. I tested this and matched all but 3 sites (Kissimmee, New Orleans Audubon and Red Rock NV) to GHCND identifications. With a change of one digit, New Orleans Audubon and Kissimmee can be matched to GHCND series. The GHCND station inventory seems to missing NV stations from the last half of the alphabet. Daily data for each of these stations can be downloaded from ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/daily/all by adding a prefix and suffix to the station id. For example:
I haven’t done any further tests on this yet, but spot checking of some clusters seems quite practical. Though the basis for selection of these comparisons seems very unclear. See related posts here and here.)
Peterson, T.C., 2003: Assessment of urban versus rural in situ surface temperatures in the contiguous United States: no difference found. J. Clim., 16, 2941—2959.